I mean it seriously was never done. Even those autocratic parties that named themselves communist parties never said that they reached communism. It was always the goal to work towards.

An easy to remember analogy is: communism is to socialism what the paradise is to Christianity.
A holy land promised by some bearded guy, where everybody lives perfectly and no bad things happen. And since it is so perfect, we are justified in killing and subjugating everyone in order to bring them also to this promised land, they will come around when they reach it.